ES6 实现递归压缩图片

相信很多人前端在上传图片时，为了优化性能，都会做一个图片压缩的功能，这里提供一段压缩代码，采用ES6标准书写。希望大家采纳指点。

html代码：

<html>
   <body>　　　
        <div class="form-upload"> 
　　　　　　<input type="file" name="logo" hidden="hidden" accept="image/*" />
　　　　　</div> 
　　</body>
</html>

js代码:

/**
 * @file CompressImg
 * @author (zhangx@nsw88.com)
 * @param file 需要压缩的图片流
 * @param ratio 单次压缩率
 * @param maxSize 压缩最大极限
 */
class Compress {
    constructor(file, ratio = 0.6, maxSize = 100*1024){
        this.time = 0;  //压缩次数
        this.file = file;
        this.ratio = ratio;
        this.maxSize = maxSize;
        this.reader = new FileReader();
    }
    async init(){
        let {file} = this;
        if( this.file.size > this.maxSize){
            this.time++;
            this.file = await this.compressing(file);
        }
        //此处实现递归压缩，但是图片多次压缩后破损，暂时实现压缩一次，后期再改动
        if( this.file.size > this.maxSize && this.time < 1){
            this.file = await this.init()
        } else {
            return this.file;
        }
    }
    async compressing(file){ //图片压缩方法
        let bold = await new Promise((resolve, reject)=>{
            this.reader.onload = e =>{
                var src = e.target.result;
                resolve(this.canvasData(src))
            }
            this.reader.onerror = err => {  
                reject(err)   
            }; 
            this.reader.readAsDataURL(file);
        });
        return bold;
    }
    async canvasData(src){  //绘制canvas图片，输出压缩图片流
        let path = src, bold = null;
        bold = await new Promise((resolve, reject) => {
            var img = new Image();
            img.src = path;
            img.onload = e => {
                let {width,height} = e.target;
                let canvas = document.createElement('canvas');
                let ctx = canvas.getContext('2d');
                canvas.width = width;
                canvas.height = height;
                ctx.drawImage(e.target, 0, 0, width,height);
                canvas.toBlob(blob => {
                    resolve(blob)
                }, "image/jpeg", this.ratio);
            }
        })
        return bold;
    }
}
export default Compress;

//压缩调
var file = document.querySelector('.form-upload input').files[0];
用let cfile= await new Compress(file).init();
posted @ 2018-03-06 17:47  degrees  阅读(434)  评论(1)  编辑  收藏  举报